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Title: Controlling proton movement: electrocatalytic oxidation of hydrogen by a nickel( ii ) complex containing proton relays in the second and outer coordination spheres

Abstract

A nickel bis(diphosphine) complex containing proton relays in the second and outer coordination spheres, Ni(PCy2N(CH2)2OMe)2, (PCy2N(CH2)2OMe = 1,5-di(methoxyethyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane), is an electrocatalyst for hydrogen oxidation. The addition of hydrogen to the Ni(II) complex results in rapid formation of three isomers of the doubly protonated Ni(0) complex, [Ni(PCy2N(CH2)2OMe2H)2]2+. The three isomers show fast intramolecular interconversion at 40 °C, unique to this complex in this class of catalysts. Under conditions of 1.0 atm H2 using H2O as a base, catalytic oxidation proceeds at a turnover frequency of 5 s -1 and an overpotential of 720 mV, as determined from the potential at half of the catalytic current. Compared to the previously reported Ni(PCy2NBn)2 complex, the new complex operates at a faster rate and at a lower overpotential. The results of this study indicate that the presence of the pendant methoxy group in the outer coordination sphere of the catalyst plays a key role, facilitating intramolecular proton movement prior to intermolecular proton removal required to complete the catalytic cycle. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest Nationalmore » Laboratory is operated by Battelle for the U.S. Department of Energy.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1126321
Report Number(s):
PNNL-SA-99116
Journal ID: ISSN 1477-9226; ICHBD9; KC0307010
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Dalton Transactions
Additional Journal Information:
Journal Volume: 43; Journal Issue: 7; Journal ID: ISSN 1477-9226
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Hydrogen oxidation; nickel phosphine complexes; molecular electrocatalysis

Citation Formats

Das, Parthapratim, Ho, Ming-Hsun, O'Hagan, Molly, Shaw, Wendy J., Morris Bullock, R., Raugei, Simone, and Helm, Monte L. Controlling proton movement: electrocatalytic oxidation of hydrogen by a nickel( ii ) complex containing proton relays in the second and outer coordination spheres. United States: N. p., 2014. Web. doi:10.1039/c3dt53074d.
Das, Parthapratim, Ho, Ming-Hsun, O'Hagan, Molly, Shaw, Wendy J., Morris Bullock, R., Raugei, Simone, & Helm, Monte L. Controlling proton movement: electrocatalytic oxidation of hydrogen by a nickel( ii ) complex containing proton relays in the second and outer coordination spheres. United States. https://doi.org/10.1039/c3dt53074d
Das, Parthapratim, Ho, Ming-Hsun, O'Hagan, Molly, Shaw, Wendy J., Morris Bullock, R., Raugei, Simone, and Helm, Monte L. Wed . "Controlling proton movement: electrocatalytic oxidation of hydrogen by a nickel( ii ) complex containing proton relays in the second and outer coordination spheres". United States. https://doi.org/10.1039/c3dt53074d.
@article{osti_1126321,
title = {Controlling proton movement: electrocatalytic oxidation of hydrogen by a nickel( ii ) complex containing proton relays in the second and outer coordination spheres},
author = {Das, Parthapratim and Ho, Ming-Hsun and O'Hagan, Molly and Shaw, Wendy J. and Morris Bullock, R. and Raugei, Simone and Helm, Monte L.},
abstractNote = {A nickel bis(diphosphine) complex containing proton relays in the second and outer coordination spheres, Ni(PCy2N(CH2)2OMe)2, (PCy2N(CH2)2OMe = 1,5-di(methoxyethyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane), is an electrocatalyst for hydrogen oxidation. The addition of hydrogen to the Ni(II) complex results in rapid formation of three isomers of the doubly protonated Ni(0) complex, [Ni(PCy2N(CH2)2OMe2H)2]2+. The three isomers show fast intramolecular interconversion at 40 °C, unique to this complex in this class of catalysts. Under conditions of 1.0 atm H2 using H2O as a base, catalytic oxidation proceeds at a turnover frequency of 5 s-1 and an overpotential of 720 mV, as determined from the potential at half of the catalytic current. Compared to the previously reported Ni(PCy2NBn)2 complex, the new complex operates at a faster rate and at a lower overpotential. The results of this study indicate that the presence of the pendant methoxy group in the outer coordination sphere of the catalyst plays a key role, facilitating intramolecular proton movement prior to intermolecular proton removal required to complete the catalytic cycle. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.},
doi = {10.1039/c3dt53074d},
url = {https://www.osti.gov/biblio/1126321}, journal = {Dalton Transactions},
issn = {1477-9226},
number = 7,
volume = 43,
place = {United States},
year = {2014},
month = {1}
}